Field
Aspects of the present invention generally relate to nuclear magnetic resonance (NMR) and, more particularly, to broadband operation of an NMR system.
Related Art
NMR systems are used to analyze material properties of a substance under test by applying an excitation magnetic field of known characteristics as stimulus to the substance during an excitation phase and by detecting a resulting magnetic field during a response phase. The detected signal is processed and analyzed to determine the material property of interest. Typical NMR systems are narrow-band systems, in which the system is designed to operate over a narrow range of frequencies. The narrowness of this range may be due to an electrically tuned circuit that is used to detect the response magnetic field produced by the sample, and may further be due to electrically tuned circuits in the electronics used to receive and process the response signal, electrically tuned circuits in the electronics use to excite the sample, and/or electrically tuned circuitry that couples the excitation and reception electronics to the circuit that detects the response magnetic fields due to the sample.
The tuning of frequencies in NMR systems have meant that analyses are limited in accuracy and energy coupling to the substance under test by how well the tuning and selection of the operational frequency matches the material characteristics of the substance. A further limitation has been the configuration of circuitry coupling the coil to the transmitter and receiver during the respective excitation and response phases. For example, active switches may be used to couple either the transmitter or the receiver to the coil during a transmit mode or receive mode respectively. The switching of the corresponding impedance of the transmitter and receiver to and from the coil result in a continual modulation of the impedance characteristics of this tuned circuit, which determines the operational frequency of the excitation or response modes. These factors collectively contribute to limitations in the effectiveness and accuracy of NMR analyses.